In recent years there has been a considerable amount of research directed to the formulation of vitamin preparations of very high potency, particularly solutions or liquids. Such high potency vitamin products may be utilized as injectable preparations, particularly in veterinary medicine, or as concentrated vitamin preparations by the pharmaceutical, food and related industries. It has been recognized that vitamin A acetate is a desirable form of vitamin A for the preparation of such injectables and liquid vitamin concentrates as it is a high potency source of vitamin A and it is less expensive than other common esters of vitamin A such as the palmitate. Vitamin A alcohol is also desirable for such preparations as it is the most potent source of vitamin A activity in terms of U.S.P. units per milligram.
The major problem inherent in the use of vitamin A acetate and vitamin A alcohol in high potency vitamin preparations is that they have a low solubility in most of the lipophilic solvent systems used to prepare high potency vitamin products of the fat soluble vitamins, e.g., vitamins A, D and E. In such preparations there is a strong tendency for vitamin A acetate and alcohol to separate from such preparations as crystals. The problem of crystallization is most pronounced with multiple vitamin preparations wherein the concentration requirements of the final product and the presence of other vitamins, preservatives and the like do not allow for the incorporation of sufficient excipients to prevent the formation of crystals of vitamin A acetate.
For example, vitamin A preparations containing 1 million units of vitamin A activity per ml. are known in the art utilizing vitamin A palmitate. For the preparation of injectable solutions with good biological mobility utilizing other vitamins, preservatives, emulsifiers and other additives, however, the use of the palmitate does not allow sufficient room in the preparation for proper quantities of these other ingredients. Vitamin A acetate, which can be incorporated into such a preparation with sufficient room for these other ingredients, unfortunately often forms crystals within a short time after the preparation is prepared. Vitamin A alcohol exhibits similar characteristics. It is manifest that a relatively low cost, ultrahigh potency vitamin A formulation utilizing the more potent vitamin A acetate would be possible if it were possible to prevent the vitamin A acetate from crystallizing out of the final preparation. It is an object of the instant invention to provide such a vitamin A preparation.